Hundreds of people have attended a demonstration in Myanmar’s northern city of Myitkyina following an attack by armed farmers on a military-inspired vigilante group as it attempted to destroy poppy fields.

Local media reported that a 660-strong crowd -- including members of the community-based anti-drug campaign group Pat Ja San -- gathered Friday outside the regional government building in Myitkyina, the capital of restive Kachin state, to protest the Thursday attack.

The protesters -- holding posters saying No More Drugs in Our Land, Government Protect Civilians and Protect Pat Jasan -- then moved to the house of powerful militia leader Zakhung Ting Ying, who they accused of owning most of the poppy fields in Wine Maw township.

On Thursday, attackers armed with guns, grenades and slingshots ambushed members of the Pat Ja San group as it began to destroy poppy fields in Pangwa and the Kan Pai Tee area of Wine Maw.

Speaking by phone to Anadolu Agency, Pat Ja San member Samson Hkalam said that at least 30 members were injured during the clashes, one of whom was wounded by gunfire.

"Some activists were attacked with landmines along the way,” he said Friday, adding that some of their cars were also burned as they made their way to the fields.

Of the 29 Pat Ja San members taken to hospital in Myitkyina he said that “two are still in critical condition”.

Protesters are now demanding that the government protect anti-drug campaigners from armed poppy farmers and militia.

Around 3,000 members of the Christian anti-drug group -- notorious for its militia-inspired hardline tactics -- had been blocked from the area by local authorities for eight days as they sought to destroy the fields.

Authorities -- who had warned that the group could be attacked -- finally allowed them to pass through Tuesday following criticism from local civil society organizations.

Pat Ja San, formed two years ago by the powerful Kachin Baptist Church, is a militia-inspired anti-drug group.

Many members wear camouflage jackets and brandish batons to deliver shock therapy to the drug-addled region.

It has been known to storm into towns wielding batons to round up drug suspects.

The group of about 100,000 members claims that most Kachin youths became drug-addicted because of the lack of law in the area.

After Afghanistan, Myanmar is the world's second-biggest producer of opium, from which heroin is derived.